Vomitoxin (Deoxynivalenol or DON) is a mycotoxin produced by a mold that infects corn, wheat, and barley. This toxic compound poses a significant threat to global agricultural economies and food safety. Vomitoxin contamination is a serious concern because it can cause health problems in livestock, particularly swine, which may experience vomiting and feed refusal. The presence of DON can also result in rejected grain shipments, discounted prices, and financial loss for producers.
The Specific Fungus Responsible
The organism responsible for producing vomitoxin in corn is the fungus Fusarium graminearum. This fungus causes Gibberella Ear Rot (GER), a disease characterized by a pink or whitish mold that usually starts at the tip of the corn ear. The mold must be present for the toxin to form, as DON is a secondary metabolite.
Secondary metabolites are compounds produced under specific environmental conditions, not for normal growth. Vomitoxin is a trichothecene mycotoxin that acts as a defense or survival compound for Fusarium graminearum. Since the fungus is widely distributed in soil and crop residue, the potential for toxin production is always present in agricultural fields.
Environmental Conditions Driving Toxin Production
The Fusarium fungus produces vomitoxin only when specific external conditions allow it to thrive and infect the corn plant. Infection is most likely during the corn’s silking and early kernel development stages, when the ear is most vulnerable. Warm and wet weather periods are particularly favorable for the fungus.
The fungus requires high moisture and moderate temperatures to infect the silks and grow into the developing kernels. High contamination risk correlates with a specific weather window: temperatures between 59 and 86 degrees Fahrenheit with relative humidity above 80% between 7 and 21 days after silking. Heavy dews, leaf wetness, and rainfall during this period aid in fungal spore dispersal and increase infection chances. If wet weather persists into the harvest season, the mold continues to grow and produce higher toxin levels.
Factors Increasing Corn Plant Susceptibility
Several factors related to the corn plant and its management increase its vulnerability to infection and toxin production. Damage to the ear, often caused by insects like the corn earworm or European corn borer, provides an easy entry point for Fusarium spores. These wounds bypass the plant’s natural defenses, allowing the fungus direct access to the moist kernels.
Genetic susceptibility to Gibberella Ear Rot varies widely among corn hybrids. Hybrids with loose or open husks at the tip are more easily infected because the silks are exposed longer. Certain agricultural practices also increase risk, such as planting corn after corn in fields where the previous crop was infected, allowing the fungus to build up in the residue. Plant stress from drought, heat, or nutrient deficiencies can weaken the plant’s immune response, making it less able to resist fungal invasion.
Preventing Vomitoxin Contamination
Managing vomitoxin contamination requires strategic planning and timely intervention.
Pre-Harvest Strategies
Selecting corn hybrids with lower susceptibility to Gibberella Ear Rot is a primary action. Planting hybrids with different maturity dates helps spread the risk, ensuring not all plants are in the vulnerable silking stage during adverse weather. Crop rotation is foundational; rotating away from corn and wheat to a non-host crop like soybeans breaks the fungus’s life cycle by reducing Fusarium residue. Residue management, including tillage, can bury infected debris and decrease the source of spores. If weather conditions favor infection during silking, timely application of specific fungicides can suppress the fungus and reduce toxin levels.
Post-Harvest Management
Post-harvest management prevents the increase of existing toxin levels. Corn should be harvested as soon as it is mature to avoid prolonged field moisture exposure. The grain must then be dried quickly to a moisture content below 15% and stored in cool, clean bins. This minimizes the environment where the mold can continue to grow and produce more DON.